What is the total oxidation number of all the atoms in phosphate ion?

The phosphate ion is PO4^3-.

Step 1: Identify the oxidation numbers of each atom.

Oxygen generally has an oxidation number of -2. Since there are four oxygen atoms, the total oxidation number for oxygen is -2*4 = -8.

Phosphorus generally has an oxidation number of +5 in compounds.

Step 2: Add the oxidation numbers together.

The total oxidation number of all the atoms in the phosphate ion is the sum of the oxidation numbers of phosphorus and oxygen, which is +5 + (-8) = -3.

This is consistent with the charge of the phosphate ion, which is -3. Therefore, the total oxidation number of all the atoms in the phosphate ion is -3.